\begin{table}%T1
\caption{JPL DE200 ephemeris of PSR B1937+21
(data from Effelsberg and WSRT observations).
 \label{tab1}}
%\centerline
{%\fontsize{8}{11}\selectfont
\begin{tabular}{ll}
\hline\hline \noalign{\smallskip} {Parameter} &  {Value}
 \\
\hline \noalign{\smallskip}
 Right Ascension (J2000) & $19^{\rm h}$
$39^{\rm m}$ 38\fs560096(6)    \\
 Declination (J2000) &
$21^\circ$ $34'$ 59\farcs13552(13) \\
 Proper motion in RA (mas yr$^{-1}$) & $-0.05(2)$ \\
 Proper motion in Dec (mas yr$^{-1}$) & $-0.47(4)$ \\
 Frequency (Hz) & 641.928244534462(3) \\
 Frequency derivative (Hz s$^{-1}$) & $-4.331046(13)\times 10^{-14}$ \\
 Frequency 2nd derivative (Hz s$^{-2}$) & $8.9(1.8)\times 10^{-27}$ \\
 Epoch of the period (MJD) & 52328.0 \\ DM (cm$^{-3}$ pc) & 71.02666(16) \\
 DM derivative (pc cm$^{-3}$ yr$^{-1}$) & $-2.10(17)$  \\
 Epoch validity start/end (MJD) & 50360 -- 52867 \\
 Epoch of arrival time$^\dagger$ (MJD) & 52332.167314839268(11) \\
 Frequency of arrival time (MHz) & 1409.300  \\
 Post-fit timing rms (ns) & 910 \\
 \noalign{\smallskip} \hline
\end{tabular}}
\par
\medskip
Note: Uncertainties quoted are in the last digit(s) and represent
$2\sigma$ estimates (twice the formal {\sc tempo} errors).  The
Epoch of arrival time refers to the maximum of the main peak in
the integrated radio profile.\\
 $^\dagger$ At Effelsberg telescope.
\end{table}